Self-laying track-type work machines are supported and propelled by an undercarriage assembly which includes an endless track chain having a plurality of interconnected articulated components. The undercarriage assembly generally includes a plurality of track supporting rollers which guide the endless track and support it as it travels over various ground conditions. Traditionally, tracked undercarriage has been designed to avoid a track roller spacing which is equal to the track pitch, or multiples of the track pitch. This is done primarily to avoid harmonic vibrations which are produced by the track rollers "timing" with the track chain articulation joints.
Vehicle vibrations and shocks are often generated when a load bearing track roller contacts a discontinuity in the track chain, such as the articulation joint between adjacent track chain components. If the born load is not supported by the articulation joint, the load must be picked up, or supported, by an adjacent track roller. If machine displacement occurs before the load is supported by other rollers, a vibration or shock is induced into the machine. Such vibrations and shock loads produce discomfort to the machine operator and reduce the useful life of some machine components.
Certain types of tracked machines require that the track supporting rollers be bogied to provide a ride leveling feature. Also, some types of tracked machines have the vertical center of gravity significantly offset from the geometric center of the track system. When bogied roller arrangements are used on machines with such offset center of gravity, it is difficult to maintain load carrying and vertically stable track rollers on both sides of the center of gravity at all times. If, as is often the case, there is only a single pair of bogied track rollers behind the center of gravity, a tipping or vertical displacement of the machine will occur when either of the bogie rollers lose track rail support as they traverse over a track link articulation joint.
Some existing tracked machines have utilized fixed, or non-pivoting, rollers in conjunction with a bogied roller arrangement. Other machines have used a multiple roller bogie system with one roller located somewhat near the bogie pivot center. However, these roller arrangements, and other roller systems on current machines, create vertical displacement and vibrations in the machines.
The present invention is directed to overcoming one or more of the problems as set forth above.